The general aims of the proposed research are to further elucidate the basic interrelationships which exist among the CNS, the pituitary release of LH/FSH, the ovary and the sex steroid feedback mechanisms which modulate these events. To this end the specific aims of the program are: 1. To continue our studies on the feedback action of LH, FSH, HCG on the concentration changes in LHRH within the medial basal hypothalamus (MBH). Presumably LH acts to activate peptidases in MBH which degrade LHRH. This event results in the cessation of LH release by the pituitary. Simultaneously MBH-LHRH precipitously declines and only reaccumulates after LH plasma levels reach baseline. Are these effects specific to LH? Using peptidase inhibitors such as Trasylol (Bayer A.G.) or altered gonadotropins such as carbohydrate-modified HCG or CL derived peptides which inhibit LH binding to receptors we plan an indepth study of these events. 2. To continue our studies on the selective release of FSH following CNS electrochemical stimulation. By progressive stimulation from the dorsal anterior preoptic area posteriorly to the dorsal medial nucleus we wish to obtain more complete neuroanatomic localization of the regions causing selective release of FSH. Concomitant with these studies will be an exploration of the causes for the selective release of FSH following CNS stimulation, or castration or LH pulse injections into proestrous rats. What ovarian secretion products are removed after ovariectomy or LH injection which results in the rapid and selective release of FSH. Are these events mediated at the pituitary, median eminence or higher CNS levels? What changes occur in MBH-LHRH following CNS stimulation, etc? 3. To attempt to examine the changes provoked by a variety of experimental manipulations on the subcellular changes in LHRH employing synaptosomal preparations from the preoptic area, and medial basal hypothalamic region. 4. To further elucidate the role of the catechol and indol amines in the regulation of LH-RH release. 5. To continue our studies on the role of estrogen and/or progresterone in regulating the ovulatory discharge of LH and/or FSH.